Python 3 - Second Edition

14.2    Counting Frequencies

It often happens that you’re interested in the frequency distribution of the elements of an iterable object—for example, how often individual letters occur in a string.[ 62 ] This problem can be elegantly solved with a dictionary:

>>> t = "This is the text">>> d = {}>>> for c in t:...     if c in d:...         d[c] += 1...     else:...         d[c] = 1...>>> d{'T': 1, 'h': 2, 'i': 2, 's': 2, ' ': 3, 't': 3, 'e': 2, 'x': 1}  

The Counter data type of the collections module is a dictionary that returns the value 0 when a key is accessed that does not exist. This data type can be used to simplify the code shown previously:

>>> t = "This is the text">>> d = collections.Counter()>>> for c in t:...     d[c] += 1...>>> dCounter({' ': 3, 't': 3, 'h': ...